/*
 * Copyright (C) 2014 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.github.ykrank.androidtools.guava;


import android.support.annotation.Nullable;

import java.util.Arrays;

import io.reactivex.annotations.CheckReturnValue;

import static com.github.ykrank.androidtools.guava.Preconditions.checkNotNull;


/**
 * Helper functions that operate on any {@code Object}, and are not already provided in
 * {@link java.util.Objects}.
 * <p>
 * <p>See the Guava TrackUser Guide on <a
 * href="https://github.com/google/guava/wiki/CommonObjectUtilitiesExplained">writing
 * {@code Object} methods with {@code MoreObjects}</a>.
 *
 * @author Laurence Gonsalves
 * @since 18.0 (since 2.0 as {@code Objects})
 */
public final class MoreObjects {
    /**
     * Returns the first of two given parameters that is not {@code null}, if either is, or otherwise
     * throws a {@link NullPointerException}.
     * <p>
     * <p><b>Note:</b> if {@code first} is represented as an {@link Optional}, this can be
     * accomplished with {@link Optional#or(Object) first.or(second)}. That approach also allows for
     * lazy evaluation of the fallback instance, using {@link Optional#or(Supplier)
     * first.or(supplier)}.
     *
     * @return {@code first} if it is non-null; otherwise {@code second} if it is non-null
     * @throws NullPointerException if both {@code first} and {@code second} are null
     * @since 18.0 (since 3.0 as {@code Objects.firstNonNull()}).
     */
    @CheckReturnValue
    public static <T> T firstNonNull(@Nullable T first, @Nullable T second) {
        return first != null ? first : checkNotNull(second);
    }

    /**
     * Creates an instance of {@link ToStringHelper}.
     * <p>
     * <p>This is helpful for implementing {@link Object#toString()}.
     * Specification by example: <pre>   {@code
     *   // Returns "ClassName{}"
     *   MoreObjects.toStringHelper(this)
     *       .toString();
     * <p>
     *   // Returns "ClassName{x=1}"
     *   MoreObjects.toStringHelper(this)
     *       .add("x", 1)
     *       .toString();
     * <p>
     *   // Returns "MyObject{x=1}"
     *   MoreObjects.toStringHelper("MyObject")
     *       .add("x", 1)
     *       .toString();
     * <p>
     *   // Returns "ClassName{x=1, y=foo}"
     *   MoreObjects.toStringHelper(this)
     *       .add("x", 1)
     *       .add("y", "foo")
     *       .toString();
     * <p>
     *   // Returns "ClassName{x=1}"
     *   MoreObjects.toStringHelper(this)
     *       .omitNullValues()
     *       .add("x", 1)
     *       .add("y", null)
     *       .toString();
     *   }}</pre>
     * <p>
     * <p>Note that in GWT, class names are often obfuscated.
     *
     * @param self the object to generate the string for (typically {@code this}), used only for its
     *             class name
     * @since 18.0 (since 2.0 as {@code Objects.toStringHelper()}).
     */
    @CheckReturnValue
    public static ToStringHelper toStringHelper(Object self) {
        return new ToStringHelper(self.getClass().getSimpleName());
    }

    /**
     * Creates an instance of {@link ToStringHelper} in the same manner as {@link
     * #toStringHelper(Object)}, but using the simple name of {@code clazz} instead of using an
     * instance's {@link Object#getClass()}.
     * <p>
     * <p>Note that in GWT, class names are often obfuscated.
     *
     * @param clazz the {@link Class} of the instance
     * @since 18.0 (since 7.0 as {@code Objects.toStringHelper()}).
     */
    @CheckReturnValue
    public static ToStringHelper toStringHelper(Class<?> clazz) {
        return new ToStringHelper(clazz.getSimpleName());
    }

    /**
     * Creates an instance of {@link ToStringHelper} in the same manner as {@link
     * #toStringHelper(Object)}, but using {@code className} instead of using an instance's {@link
     * Object#getClass()}.
     *
     * @param className the name of the instance type
     * @since 18.0 (since 7.0 as {@code Objects.toStringHelper()}).
     */
    @CheckReturnValue
    public static ToStringHelper toStringHelper(String className) {
        return new ToStringHelper(className);
    }

    /**
     * Support class for {@link MoreObjects#toStringHelper}.
     *
     * @author Jason Lee
     * @since 18.0 (since 2.0 as {@code Objects.ToStringHelper}).
     */
    public static final class ToStringHelper {
        private final String className;
        private ValueHolder holderHead = new ValueHolder();
        private ValueHolder holderTail = holderHead;
        private boolean omitNullValues = false;

        /**
         * Use {@link MoreObjects#toStringHelper(Object)} to create an instance.
         */
        private ToStringHelper(String className) {
            this.className = checkNotNull(className);
        }

        /**
         * Configures the {@link ToStringHelper} so {@link #toString()} will ignore
         * properties with null value. The order of calling this method, relative
         * to the {@code add()}/{@code addValue()} methods, is not significant.
         *
         * @since 18.0 (since 12.0 as {@code Objects.ToStringHelper.omitNullValues()}).
         */
        public ToStringHelper omitNullValues() {
            omitNullValues = true;
            return this;
        }

        /**
         * Adds a name/value pair to the formatted output in {@code name=value}
         * format. If {@code value} is {@code null}, the string {@code "null"}
         * is used, unless {@link #omitNullValues()} is called, in which case this
         * name/value pair will not be added.
         */
        public ToStringHelper add(String name, @Nullable Object value) {
            return addHolder(name, value);
        }

        /**
         * Adds a name/value pair to the formatted output in {@code name=value}
         * format.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
         */
        public ToStringHelper add(String name, boolean value) {
            return addHolder(name, String.valueOf(value));
        }

        /**
         * Adds a name/value pair to the formatted output in {@code name=value}
         * format.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
         */
        public ToStringHelper add(String name, char value) {
            return addHolder(name, String.valueOf(value));
        }

        /**
         * Adds a name/value pair to the formatted output in {@code name=value}
         * format.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
         */
        public ToStringHelper add(String name, double value) {
            return addHolder(name, String.valueOf(value));
        }

        /**
         * Adds a name/value pair to the formatted output in {@code name=value}
         * format.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
         */
        public ToStringHelper add(String name, float value) {
            return addHolder(name, String.valueOf(value));
        }

        /**
         * Adds a name/value pair to the formatted output in {@code name=value}
         * format.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
         */
        public ToStringHelper add(String name, int value) {
            return addHolder(name, String.valueOf(value));
        }

        /**
         * Adds a name/value pair to the formatted output in {@code name=value}
         * format.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
         */
        public ToStringHelper add(String name, long value) {
            return addHolder(name, String.valueOf(value));
        }

        /**
         * Adds an unnamed value to the formatted output.
         * <p>
         * <p>It is strongly encouraged to use {@link #add(String, Object)} instead
         * and give value a readable name.
         */
        public ToStringHelper addValue(@Nullable Object value) {
            return addHolder(value);
        }

        /**
         * Adds an unnamed value to the formatted output.
         * <p>
         * <p>It is strongly encouraged to use {@link #add(String, boolean)} instead
         * and give value a readable name.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.addValue()}).
         */
        public ToStringHelper addValue(boolean value) {
            return addHolder(String.valueOf(value));
        }

        /**
         * Adds an unnamed value to the formatted output.
         * <p>
         * <p>It is strongly encouraged to use {@link #add(String, char)} instead
         * and give value a readable name.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.addValue()}).
         */
        public ToStringHelper addValue(char value) {
            return addHolder(String.valueOf(value));
        }

        /**
         * Adds an unnamed value to the formatted output.
         * <p>
         * <p>It is strongly encouraged to use {@link #add(String, double)} instead
         * and give value a readable name.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.addValue()}).
         */
        public ToStringHelper addValue(double value) {
            return addHolder(String.valueOf(value));
        }

        /**
         * Adds an unnamed value to the formatted output.
         * <p>
         * <p>It is strongly encouraged to use {@link #add(String, float)} instead
         * and give value a readable name.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.addValue()}).
         */
        public ToStringHelper addValue(float value) {
            return addHolder(String.valueOf(value));
        }

        /**
         * Adds an unnamed value to the formatted output.
         * <p>
         * <p>It is strongly encouraged to use {@link #add(String, int)} instead
         * and give value a readable name.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.addValue()}).
         */
        public ToStringHelper addValue(int value) {
            return addHolder(String.valueOf(value));
        }

        /**
         * Adds an unnamed value to the formatted output.
         * <p>
         * <p>It is strongly encouraged to use {@link #add(String, long)} instead
         * and give value a readable name.
         *
         * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.addValue()}).
         */
        public ToStringHelper addValue(long value) {
            return addHolder(String.valueOf(value));
        }

        /**
         * Returns a string in the format specified by
         * {@link MoreObjects#toStringHelper(Object)}.
         * <p>
         * <p>After calling this method, you can keep adding more properties to later
         * call toString() again and get a more complete representation of the
         * same object; but properties cannot be removed, so this only allows
         * limited reuse of the helper instance. The helper allows duplication of
         * properties (multiple name/value pairs with the same name can be added).
         */
        @CheckReturnValue
        @Override
        public String toString() {
            // create a copy to keep it consistent in case value changes
            boolean omitNullValuesSnapshot = omitNullValues;
            String nextSeparator = "";
            StringBuilder builder = new StringBuilder(32).append(className).append('{');
            for (ValueHolder valueHolder = holderHead.next;
                 valueHolder != null;
                 valueHolder = valueHolder.next) {
                Object value = valueHolder.value;
                if (!omitNullValuesSnapshot || value != null) {
                    builder.append(nextSeparator);
                    nextSeparator = ", ";

                    if (valueHolder.name != null) {
                        builder.append(valueHolder.name).append('=');
                    }
                    if (value != null && value.getClass().isArray()) {
                        Object[] objectArray = {value};
                        String arrayString = Arrays.deepToString(objectArray);
                        builder.append(arrayString.substring(1, arrayString.length() - 1));
                    } else {
                        builder.append(value);
                    }
                }
            }
            return builder.append('}').toString();
        }

        private ValueHolder addHolder() {
            ValueHolder valueHolder = new ValueHolder();
            holderTail = holderTail.next = valueHolder;
            return valueHolder;
        }

        private ToStringHelper addHolder(@Nullable Object value) {
            ValueHolder valueHolder = addHolder();
            valueHolder.value = value;
            return this;
        }

        private ToStringHelper addHolder(String name, @Nullable Object value) {
            ValueHolder valueHolder = addHolder();
            valueHolder.value = value;
            valueHolder.name = checkNotNull(name);
            return this;
        }

        private static final class ValueHolder {
            String name;
            Object value;
            ValueHolder next;
        }
    }

    private MoreObjects() {
    }
}
